1. Field of the Invention
This invention relates to an external magnetic-type speaker apparatus, and more particularly to a small speaker apparatus for use in a mobile telephone or the like.
2. Description of the Related Art
Most small speakers used in mobile telephones are internal magnetic-type speakers that have limited dimensions.
For these internal magnetic-type speakers, it is possible to maintain enough space in the section that corresponds to the rear of the vibrating plate of the frame such that it is possible to form air-escape holes. Air is let to escape in this way so as not to hinder vibration of the vibrating plate.
Also, for the aforementioned kind of internal magnetic-type speakers, it is possible to maintain enough space in the section that corresponds to the rear of the vibrating plate such that it is possible to apply a damping material for acoustical resistance.
However, in the case of using this kind of conventional internal magnetic-type speaker, it is necessary to use a column-shaped piece, which has a smaller diameter than the inside of the voice coil of the magnetic circuit, as the magnet, so the size of the magnet is limited. As a result, improvement of the sensitivity is also limited.
In contrast to this, in the case of using an external magnetic-type speaker, it is necessary to use a magnet, which has a smaller diameter than the frame for forming the air-escape holes described above, so it is still impossible to increase the size of the magnet.
In order to solve the aforementioned problems, it is the objective of this invention to provide a small speaker apparatus that is capable of allowing air to escape, and that has better sensitivity than a conventional speaker.
The above object of the present invention can be achieved by a speaker apparatus provided with: a magnetic circuit having an external magnet; a dome-type vibrating plate; a frame that is located around the magnetic circuit and to which the magnetic circuit and edge of the vibrating plate are attached; and a ventilation section that is formed at a specified location in the side surface of the frame, which is nearly parallel with side surface of the magnet, for letting the air between the rear surface of the vibrating plate and the magnetic circuit escape.
According to the present invention, the speaker apparatus is provided with a frame to which a magnetic circuit and the edge of a dome-shaped vibrating plate are fastened, and where the side surface of this frame is nearly parallel with the side surface of the aforementioned magnet. In addition, there is a ventilation section at a specified location on the side surface of the frame for letting air between the rear surface of the vibrating plate and the magnetic circuit escape. Therefore, it is possible to prevent the pressure in the space between the rear surface of the vibrating plate and the magnetic circuit from becoming high, such that the vibrating plate vibrates smoothly and accurately according to an input signal. Moreover, even when using an external magnet, the position of the sides of the external magnet, or in other words the outer diameter of the external magnet, can be set on the inner wall of the side surface of the frame in which the aforementioned ventilation section is formed, and thus it is possible to use a large magnet of which the size of the dome-shaped vibrating plate is not limited. Also, sensitivity is greatly improved in comparison with a conventional speaker.
In one aspect of the present invention, said ventilation section is a window-shaped opening section that is formed in said frame.
According to this aspect, the aforementioned ventilation section is a window-shaped opening that is formed in the frame, so it is possible to prevent the pressure in the space between the rear surface of the vibrating plate and the magnetic circuit from becoming high such that the vibrating plate vibrates smoothly and accurately according to an input signal. Moreover, even when using an external magnet, the position of the sides of the external magnet, or in other words the outer diameter of the external magnet, can be set on the inner wall of the side surface of the frame in which the aforementioned ventilation section is formed, and thus it is possible to use a large magnet of which the size of the dome-shaped vibrating plate is not limited. Also, sensitivity is greatly improved in comparison with a conventional speaker. Furthermore, since the aforementioned opening is formed in a window shape, damping material can be installed easily.
In another aspect of the present invention, damping material is attached to opening section.
According to this aspect, the aforementioned opening is formed in the frame and has a window shape so it is possible to easily install damping material. By installing damping material to the opening, the damping material can be used for acoustical resistance, making it easy to perform acoustical control.
In further aspect of the present invention, said frame comprises: a first frame to which the edge of the vibrating plate is attached; and a second frame to which the magnetic circuit is attached, wherein the first frame is fastened to the second frame.
According to this aspect, the aforementioned frame is provided with a first and second frame, such that the edge of the vibrating plate is attached to the first frame, and the magnetic circuit is attached to the second frame. Moreover, the first frame and second frame are attached together. Therefore it is easy to construct a frame in which the aforementioned ventilation section is formed in the side surface. With the ventilation section described above, it is possible to prevent the pressure in the space between the rear surface of the vibrating plate and the magnetic circuit from becoming high, such that the vibrating plate vibrates smoothly and accurately according to an input signal. Moreover, even when using an external magnet, the position of the sides of the external magnet, or in other words the outer diameter of the external magnet, can be set on the inner wall of the side surface of the frame in which the aforementioned ventilation section is formed, and thus it is possible to use a large magnet of which the size of the dome-shaped vibrating plate is not limited. Also, sensitivity is greatly improved in comparison with a conventional speaker. Furthermore, since the aforementioned opening is formed in a window shape, damping material can be installed easily.
In further aspect of the present invention, the ventilation section is a window-shaped opening section that is formed by the first and second frames.
According to this aspect, the aforementioned ventilation section is an opening that is formed into a window shape by the first and second frames, so by forming a U-shaped opening on the side surface of the second frame, for example, and by attaching the first and second frames together such that the opened side is covered by the first frame, it is possible to easily form a window-shaped opening.
In further aspect of the present invention, damping material is attached to the opening section.
According to this aspect, the aforementioned opening is formed into a window shape by the first and second frames, so it is possible to easily attach damping material. Also, by attaching damping material to the opening, the damping material functions as acoustical resistance, making it possible to easily perform acoustical control.
In further aspect of the present invention, a cylindrical-shaped hollow section is formed in the center of the yoke of the magnetic circuit, and damping material is attached to the bottom of the hollow section.
According to this aspect, the yoke of the aforementioned magnetic circuit is formed with a cylindrical-shaped hollow section in the center, and the damping material is attached to the bottom of the hollow section. Air is taken into and discharged from the internal space that is formed by the rear surface of the vibrating plate and magnetic circuit, making it possible to reduce the pressure in this internal space.